Mozilla said co-founder Brendan Eich has stepped down as chief executive after less than two weeks in the role because of mounting pressure from his support of California's anti-gay marriage ballot measure.

Mozilla named the web organization's marketing chief, Chris Beard, to serve as interim chief executive, after a co-founder stepped down from that role following complaints about his opposition to gay marriage.

The Supreme Court on Tuesday will hear argument on whether same-sex couples have a constitutional right to marry nationwide. The question came to the court because a federal appeals court said four states in the Midwest could bar gay unions, creating a conflict in the federal courts where most rulings in the last two years have said gay couples have...